Variable phase shifter, semiconductor integrated circuit and phase shifting method

Abstract

A variable phase shifter. The variable phase shifter includes: a transmission line that outputs quadrature signals from a pair of output ports in response to an input signal of a specific frequency; a synthesizer that includes a first transistor connected to a first port of the pair of output ports and a second transistor connected to a second port of the pair of output ports, and that on input of the input signal takes signals output from the pair of output ports of the transmission line with a phase according to their respective load impedances and employs the first and the second transistors to amplify and combine the signals; and a phase controller that controls the phase of the output signal that is combined and output by the synthesizer by controlling the amplification operation of each of the first and second transistors of the synthesizer.

What is claimed is: 
     
       1. A variable phase shifter, comprising:
 a transmission line that outputs quadrature signals from a pair of output ports in response to an input signal of a specific frequency; 
 a synthesizer that includes a first transistor connected to a first port of the pair of output ports and a second transistor connected to a second port of the pair of output ports so that parasitic capacitance of the first transistor and the second transistor becomes load impedance for the transmission line, and that inputs signals output from the pair of output ports of the transmission line with a phase difference according to their respective load impedances, on input of the input signal, to the first transistor and the second transistor and combines the signals, which are amplified and output by the first transistor and the second transistor; and 
 a phase controller that controls the phase of the output signal that is combined and output by the synthesizer by controlling the amplification operation of each of the first and second transistors of the synthesizer. 
 
     
     
       2. The variable phase shifter of  claim 1 , wherein
 the phase controller controls bias voltages respectively applied to gates of each of the first and second transistors connected to the pair of output ports based on a target phase of the output signal. 
 
     
     
       3. The variable phase shifter of  claim 2 , wherein
 the phase controller includes:
 a power source section that outputs a stepwise set voltage; and 
 a voltage controller that controls the power source section so as to output as a bias voltage a voltage set based on the target phase from out of the stepwise set voltages. 
 
 
     
     
       4. The variable phase shifter of  claim 3 , wherein
 when from out of the stepwise set voltages a third voltage between the first voltage and the second voltage is output from the power source section as the bias voltage, the phase controller controls the output time of the first voltage and the output time of the second voltage base on the first, second and third voltages. 
 
     
     
       5. The variable phase shifter of  claim 2 , further comprising:
 an electrostatic capacitance element of specific electrostatic capacitance connected to the first or the second port of the pair of output ports so as to configure the load impedance; and 
 a switch member that switches the load impedance by disconnecting and connecting the electrostatic capacitance element from the output port to which the electrostatic capacitance element was connected, wherein 
 the phase controller controls to switch the load impedance using the switch member based on the target phase. 
 
     
     
       6. The variable phase shifter of  claim 5 , wherein
 the switch member is a third transistor, and electrostatic capacitance of the electrostatic capacitance element is parasitic capacitance of the third transistor. 
 
     
     
       7. The variable phase shifter  claim 2 , further comprising:
 a third transistor that is connected to the first or second port of the pair of output ports, and whose parasitic capacitance is added as the load impedance by ON operation of the third transistor, wherein 
 the phase controller controls switching operation of the third transistor based on the target phase. 
 
     
     
       8. A semiconductor integrated circuit, comprising:
 a variable phase shifter that includes: 
 a synthesizer that, for a transmission line that outputs quadrature signals from a pair of output ports in response to an input signal of a specific frequency, includes a first transistor connected to a first port of the pair of output ports and a second transistor connected to a second port of the pair of output ports so that parasitic capacitance of the first transistor and the second transistor becomes load impedance for the transmission line, and that inputs signals output from the pair of output ports of the transmission line with a phase difference according to their respective load impedances, on input of the input signal, to the first transistor and the second transistor and combines the signals, which are amplified and output by the first transistor and the second transistor; and 
 a phase controller that controls the phase of the output signal that is combined and output by the synthesizer by controlling the amplification operation of each of the first and second transistors of the synthesizer. 
 
     
     
       9. The semiconductor integrated circuit of  claim 8 , further comprising:
 the transmission line. 
 
     
     
       10. The semiconductor integrated circuit of  claim 8 , wherein
 the phase controller includes:
 a power source section that outputs a stepwise set voltage; and 
 a voltage controller that controls the power source section so as to output as respective bias voltages to the first and second transistors a voltage set for the target phase from out of the stepwise set voltages. 
 
 
     
     
       11. The semiconductor integrated circuit of  claim 10 , further comprising:
 an electrostatic capacitance element of specific electrostatic capacitance connected to the first or the second port of the pair of output ports so as to configure the load impedance; and 
 a switch member that switches the load impedance by disconnecting and connecting the electrostatic capacitance element from the output port to which the electrostatic capacitance element was connected, wherein 
 the phase controller controls to switch the load impedance using the switch member based on the target phase. 
 
     
     
       12. The semiconductor integrated circuit of  claim 11 , wherein
 the switch member is a third transistor, and electrostatic capacitance of the electrostatic capacitance element is parasitic capacitance of the third transistor. 
 
     
     
       13. The semiconductor integrated circuit of  claim 10 , further comprising:
 a third transistor that is connected to the first or second port of the pair of output ports, and whose parasitic capacitance is added as the load impedance by ON operation of the third transistor, wherein 
 the phase controller controls switching operation of the third transistor based on the target phase. 
 
     
     
       14. A phase shifting method, comprising:
 for a transmission line that outputs quadrature signals from a pair of output ports in response to an input signal of a specific frequency, connecting a first transistor to a first port of the pair of output ports and connecting a second transistor (Mb) to a second port of the pair of output ports so that parasitic capacitance of the first transistor and the second transistor becomes load impedance for the transmission line; 
 inputting signals output from the pair of output ports of the transmission line with a phase difference according to the their respective load impedance, on input of the input signal, to the first transistor and the second transistor, and combining the signals, which are amplified and output by the first transistor and the second transistor; and 
 controlling the phase of the combined output signal by controlling the amplification operation of each of the first and second transistors. 
 
     
     
       15. The phase shifting method of  claim 14 , wherein
 the phase and amplitude of the output signal is controlled by controlling respective bias voltages applied to gates of the first and second transistors connected to the pair of ports. 
 
     
     
       16. The phase shifting method of  claim 14 , further comprising:
 connecting an electrostatic capacitance element of specific electrostatic capacitance to the first or the second port of the pair of output ports; 
 connecting a switch member so as to disconnect and connect the electrostatic capacitance element from the output port to which the electrostatic capacitance element was connected; and 
 switching the load impedance using the switch member based on a target phase. 
 
     
     
       17. The phase shifting method of  claim 16 , wherein
 a third transistor is employed as the switch member so that parasitic capacitance configures electrostatic capacitance of the electrostatic capacitance element. 
 
     
     
       18. The phase shifting method of  claim 14 , further comprising:
 connecting a third transistor to the first or second port of the pair of output ports so that parasitic capacitance is added as the load impedance by ON operation of the third transistor; and 
 controlling switching operation of the third transistor based on the target phase.